The present invention relates to a dual SIP (Single In-Line Package) package from a pair of individual SIP leadframes and to encapsulating components such as transient voltage suppressor chips in the dual SIP package.
SIP (Single In-Line Package) structures are well-known. An SIP leadframe 1 is shown in FIG. 1 with a plurality of conductor chips and/or other components) attached thereto. The leadframe includes a metal support strip 1A and a plurality of perpendicular leads 1B. Dotted line 6 indicates that the support strip is clipped off after manufacture of the SIP package has been completed. An enlarged metal pad 1C is attached to and integral with the outer end of each of the leads 1B. A semiconductor chip 3 (or other component such as a capacitor) is attached to each pad 1C. Various bonding wires such as 4 are attached between bonding areas of the various chips/components 3.
The portion of the leadframe including the pads 1C, chips 3, bonding wires 4, and a portion of the leads 1B is encapsulated in plastic 5 using various conventional techniques. The support strip IA is clipped away along dotted line 6, and if desired, the ends of the leads IB are suitably bent. The leads then can be soldered to a printed circuit board or other elements. Such prior art using bonding wires results in unacceptable transient voltage suppression due to the inherent parasitic resistance and inductance of the bonding wires. There exist prior art schemes using continuous bars instead of bonding wires. These schemes reduce such parasitic inductance and resistance but severely limit the possible circuit topologies, and use up one pad location only for making electrical connection back to the SIP lead frame by using a short cell.
There is a substantial need for semiconductor components containing high power chips (such as the assignee's TRANSZORB transient voltage suppressor chips which are capable of dissipating transient high power) small enough to fit into small spaces, for example on a small crowded printed circuit board disposed within a cable connector housing having a large number of individual signal conductors each of which needs to be protected from transient voltages.
At the present state of the art, the main commercially available choices for transient voltage suppressors include those mounted in so-called axial lead packages, in which the two leads of a transient voltage suppressor extend in opposite directions along a common axis. These devices are usually physically large, and have a large "footprint", that is, when installed on a printed circuit board, they cover a large amount of area of the printed circuit board. Other transient voltage suppressors are packaged in DIP Packages (Dual In-line Packages), but such devices typically are incapable of dissipating enough power to result in reliable transient voltage suppression. Furthermore, such devices typically have large lead inductance which interfere with effective suppression of large, high speed transient voltages. Surface mount packages also are available; they typically have a large "footprint", and are not suitable for "high density" applications in which a number of high power transient voltage suppressors are required in a very small volume, such as in a multiconductor cable connector or adapter.
There remains a need for a transient voltage suppressor package for encapsulating a large number of high power transient voltage suppressor devices and also capable of being housed in a small volume, and providing low parasitic lead inductance.